By Scott Nelson Updated Mar 24, 2022
A compound’s polarity arises from the unequal sharing of electrons between its constituent atoms. When one atom exerts a stronger electron‑pulling force—its electronegativity—than its partner, a dipole moment develops, rendering the molecule polar. Additionally, the spatial arrangement, or symmetry, of atoms influences polarity. Typically, chemists use Lewis dot or valence‑bond diagrams to visualize electron distribution and assess polarity.
Sketch the Lewis structure based on the valence electrons of each atom.
Identify lone pairs and apply the VSEPR model to predict the molecule’s geometry.
Refer to the periodic table to assign electronegativity values to each atom, then compute the relative differences across bonds.
Evaluate bond character—hydrogen bonding, ionic, or covalent—to understand how it affects charge distribution.
Determine the overall dipole by adding vector contributions of individual bond moments, or by noting that symmetrical arrangements cancel out, leaving a non‑polar molecule.
Symmetry often reveals polarity at a glance. Linear molecules are typically non‑polar, while bent molecules like water exhibit strong polarity.
